1. Field of the Invention
The present invention relates to a method and apparatus for processing biological fluids into their therapeutically valuable components. More particularly, the present invention relates to a method and apparatus for processing donated blood into its therapeutically valuable components. Most particularly, the present invention relates to an improved method and apparatus for processing donated blood into its therapeutically valuable components which uses improved open-loop and closed-loop systems to substantially increase the recovery of all the blood products from the donated blood.
2. Discussion of the Related Art
Methods and apparatus for processing blood are well known in the prior art. U.S. Pat. No. 3,892,236 to Djerassi shows an apparatus for the continuous withdrawal of blood from a human donor, forced extracorporeal circulation of blood of the donor with separation of granulocytes, and return by gravity of the leukocyte-poor whole blood to the donor.
U.S. Pat. No. 5,126,054 to Matkovich shows a venting means for venting gas from the transfer line of a liquid delivery system comprising a housing, a first, liquid-wettable, microporous membrane carried in said housing so as to be in communication with the transfer line, and a second, non-liquid-wettable, gas permeable microporous membrane superimposed on said microporous membrane to the outward side of the housing. Gas in the delivery system is vented from the system so long as the first microporous membrane remains unwetted by the delivery liquid.
U.S. Pat. No. 5,451,321 to Matkovich shows biological fluid processing assemblies having a gas inlet, and/or a gas outlet.
While these devices are generally satisfactory, some of the methods and apparatus of the prior art leaves a large amount of biological fluid trapped in various elements of the fluid processing apparatus. While the aforementioned patent 5,451,321 to Matkovich provides for liquid trapped in various elements of the blood processing system to be recovered either by causing a volume of gas behind the entrapped liquid to push the liquid through those elements and into the designated collection bag, or by pulling the entrapped liquid into the designated collection bag by a pressure differential (e.g. gravity head, pressure cuff, suction and the like), the system still has several drawbacks. One drawback is that they require one or more nonwettable, gas permeable, membranes. This requirement can lead to increased costs over wettable membranes.
Therefore, those skilled in the art continue to search for a method and apparatus to provide for optimal recovery of the biological fluid from biological fluid processing systems, cost reduction and ease of use, and have developed novel open and closed loop systems and methods associated therewith to achieve this goal.